JEE Main - Alkynes acidic character addition reactions and polymerization Online Test (MCQ Quiz)

1. Which of the following is the most acidic alkyne?

A) Ethyne B) Propyne C) 1-Butyne D) 2-Butyne

2. The acidic nature of terminal alkynes is due to:

A) The presence of a pi bond B) The high s-character of the sp hybridized carbon atom C) The electronegativity of the hydrogen atom D) The resonance stabilization of the conjugate base

3. Which reagent is commonly used to deprotonate terminal alkynes?

A) Sodium hydroxide (NaOH) B) Sodium amide (NaNH2) C) Water (H2O) D) Ammonia (NH3)

4. The conjugate base of ethyne is called:

A) Acetylide ion B) Vinyl anion C) Ethynyl anion D) Carbanion

5. Which of the following reactions demonstrates the acidic character of alkynes?

A) Electrophilic addition of HBr B) Reaction with sodium amide in liquid ammonia C) Hydroboration-oxidation D) Ozonolysis

6. Terminal alkynes can react with heavy metal ions like silver (Ag+) and copper(I) (Cu+) to form:

A) Alkenes B) Alkanes C) Explosive metal acetylides D) Ethers

7. The reaction of a terminal alkyne with a strong base like NaNH2 followed by an alkyl halide (R-X) is an example of:

A) Electrophilic substitution B) Nucleophilic addition C) Nucleophilic substitution (alkylation) D) Oxidation

8. Which of the following is NOT a product of the addition of HBr to ethyne?

A) Vinyl bromide B) 1,1-Dibromoethane C) 1,2-Dibromoethane D) Bromoethane

9. When ethyne reacts with excess HBr, the product formed is:

A) Vinyl bromide B) 1,1-Dibromoethane C) 1,2-Dibromoethane D) Ethane

10. The addition of halogens (e.g., Br2) to alkynes follows:

A) Markovnikov's rule B) Anti-Markovnikov's rule C) Anti-addition mechanism D) Syn-addition mechanism

11. Addition of H2O to ethyne in the presence of HgSO4 and dil. H2SO4 yields:

A) Ethanol B) Acetaldehyde C) Acetic acid D) Ethane

12. The hydration of an unsymmetrical alkyne like propyne follows Markovnikov's rule, leading to the formation of a(n):

A) Aldehyde B) Ketone C) Carboxylic acid D) Alcohol

13. Hydroboration-oxidation of a terminal alkyne results in the formation of:

A) An aldehyde B) A ketone C) A carboxylic acid D) An ester

14. The reaction of ethyne with hydrogen gas in the presence of a catalyst like Pd/BaSO4 (Lindlar's catalyst) produces:

A) Ethane B) Ethene C) Acetylene D) Ethanal

15. Which catalyst is used for the partial reduction of alkynes to cis-alkenes?

A) Raney Nickel B) Platinum dioxide C) Lindlar's catalyst D) Palladium on charcoal

16. Dissolving metal reduction (e.g., Na in liquid NH3) of an alkyne yields:

A) cis-Alkene B) trans-Alkene C) Alkane D) Alkyne

17. Ozonolysis of ethyne followed by reductive workup yields:

A) Glyoxal B) Oxalic acid C) Ethylene glycol D) Acetic acid

18. Polymerization of ethyne leads to the formation of:

A) Polyethylene B) Polyvinyl chloride C) Polyacetylene D) Polystyrene

19. Which of the following conditions favors polymerization of alkynes?

A) Low temperature and high pressure B) High temperature and presence of catalysts C) Low temperature and absence of catalysts D) High pressure and absence of catalysts

20. The acidic hydrogen in ethyne can be replaced by:

A) A methyl group B) A hydroxyl group C) A halogen atom D) All of the above

21. The reaction of ethyne with hot concentrated sulfuric acid leads to:

A) Benzene B) Ethene C) Ethanal D) Ethanoic acid

22. Which of the following is a characteristic reaction of terminal alkynes that distinguishes them from internal alkynes?

A) Electrophilic addition of H2 B) Addition of halogens C) Formation of metal acetylides with Ag+ or Cu+ D) Hydration

23. The product of the reaction of propyne with NaNH2 followed by CH3I is:

A) 2-Butyne B) 1-Butyne C) 1-Butene D) 2-Butene

24. Which type of bond is broken during the addition of HBr to ethyne?

A) Sigma bond B) Pi bond C) Both sigma and pi bonds D) Only one of the pi bonds

25. The rate of deprotonation of alkynes with a base increases in the order:

A) Ethyne < Propyne < 1-Butyne B) Ethyne > Propyne > 1-Butyne C) Propyne > Ethyne > 1-Butyne D) 1-Butyne > Propyne > Ethyne

26. The structure of the acetylide ion formed from ethyne is:

A) CH3-C≡C- B) HC≡C- C) CH2=C=CH- D) CH3-C=C-

27. Which of the following can be synthesized using the alkylation of terminal alkynes?

A) Alkanes B) Primary alcohols C) Internal alkynes D) Ethers

28. The reaction of ethyne with dilute H2SO4 and HgSO4 is an example of:

A) Electrophilic addition B) Nucleophilic addition C) Free radical addition D) Cycloaddition

29. What is the intermediate formed during the hydration of ethyne before tautomerization?

A) Vinyl alcohol B) Ethanal C) Ethene D) Acetaldehyde hydrate

30. The anti-Markovnikov addition of water to alkynes is achieved by:

A) HgSO4/dil. H2SO4 B) BH3 followed by H2O2/OH- C) Br2/H2O D) HCl

31. The reduction of an alkyne with Na/NH3 (liquid) yields a mixture of cis and trans alkenes.

A) True, primarily trans alkene is formed. B) True, primarily cis alkene is formed. C) False, only cis alkene is formed. D) False, only trans alkene is formed.

32. Which catalyst is used for the complete reduction of alkynes to alkanes?

A) Lindlar's catalyst B) Pd/BaSO4 C) Raney Nickel or Pt/Pd D) Na/NH3

33. The ozonolysis of propyne followed by reductive workup yields:

A) Acetaldehyde and formaldehyde B) Pyruvic acid and formaldehyde C) Acetic acid and formaldehyde D) Glyoxal and formaldehyde

34. The polymerization of ethyne can produce conjugated polymers with interesting electronic properties.

A) True, such polymers are called polyalkynes. B) True, such polymers are called polyenes. C) False, ethyne does not polymerize. D) False, only alkenes polymerize.

35. Which of the following is a consequence of the sp hybridization of carbon atoms in alkynes?

A) Increased bond length between carbon atoms B) Decreased bond angle C) Increased acidity D) Decreased reactivity towards electrophiles

36. Reaction of acetylene with hot concentrated nitric acid results in the formation of:

A) Nitroacetylene B) Benzene C) Oxalic acid D) Carbon dioxide

37. Which statement is FALSE regarding the acidic character of alkynes?

A) Ethyne is more acidic than ethene. B) Terminal alkynes are more acidic than internal alkynes. C) The conjugate base of ethyne is more stable than the conjugate base of ethene. D) Acidity decreases with increasing s-character of the hybrid orbital.

38. When ethyne reacts with one equivalent of Br2, the product is:

A) 1,1-Dibromoethane B) 1,2-Dibromoethane C) Bromoethene D) Vinyl bromide

39. The formation of a precipitate with ammoniacal silver nitrate solution is a test for:

A) Internal alkynes B) Terminal alkynes C) Alkenes D) Alkanes

40. The addition of H2O to 1-butyne in the presence of HgSO4 and dil. H2SO4 will yield:

A) 1-Butanol B) 2-Butanol C) 1-Butanone D) 2-Butanone

41. The reaction where an alkyne is converted to a cis-alkene using a poisoned palladium catalyst is known as:

A) Dissolving metal reduction B) Catalytic hydrogenation C) Lindlar reduction D) Ozonolysis

42. Ozonolysis of 2-butyne followed by workup yields:

A) Acetaldehyde B) Pyruvic acid C) Two molecules of acetaldehyde D) Two molecules of pyruvic acid

43. The polymerization of alkynes can be catalyzed by:

A) Lewis acids B) Transition metal complexes C) Protic acids D) All of the above

44. Which of the following is a property of the sp hybridized carbon atom in alkynes?

A) It is less electronegative than sp2 hybridized carbon. B) It has a bond angle of 120 degrees. C) It has 50% s-character. D) It forms longer bonds than sp2 hybridized carbon.

45. The reaction of ethyne with dilute nitric acid and mercuric nitrate yields:

A) Mercury acetylide B) Nitroacetylene C) Benzene D) Acetaldehyde

46. Which of the following terminal alkynes is the most acidic?

A) Phenylacetylene B) 1-Butyne C) Propyne D) Ethyne

47. The addition of one mole of HBr to 1-butyne follows Markovnikov's rule and produces:

A) 1-Bromo-1-butene B) 1-Bromo-2-butene C) 2-Bromo-1-butene D) 2-Bromo-2-butene

48. The conversion of an alkyne to a trans-alkene can be achieved by using:

A) Lindlar's catalyst B) Pd/C C) Na in liquid NH3 D) H2/Ni

49. Acid-catalyzed hydration of internal alkynes like 2-butyne yields:

A) An aldehyde B) A ketone C) A mixture of aldehyde and ketone D) A carboxylic acid

50. The polymerization of ethyne to polyacetylene is a type of:

A) Addition polymerization B) Condensation polymerization C) Chain growth polymerization D) Step growth polymerization

Alkynes acidic character addition reactions and polymerization - Online Test

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